Tubular incandescent lamp having improved filament support

ABSTRACT

A tubular, double ended electric incandescent lamp has one or more improved support members intermediate the ends of a coiled lamp filament to support the filament from the lamp envelope walls and to maintain the filament at about the axis of the lamp envelope. Each support member comprises a plurality of intertwisted wires, each of which partially encircles the filament. The ends of the intertwisted wires bear against the lamp envelope radially.

United States Patent 1191 McNeill et a1.

1 Jan. 1, 1974 TUBULAR INCANDESCENT LAMP HAVING IMPROVED FILAMENT SUPPORT [75] Inventors: Frederick J. McNeill, Londonderry,

N.l-l.; Joseph S. Kulik, Jr.,

Amesbury, Masss, David L. Smith, Sr., Nashua, NH.

[73] Assignee: GTE Sylvania Incorporated,

Danvers, Mass.

[22] Filed: Nov. 2, 1972 [2]] Appl. No.: 303,035

[52] US. Cl. 313/274, 313/286 [51] Int. Cl H0lj 1/96, H01j 19/50 [58] Field of Search 313/271, 274, 286

[56] References Cited UNITED STATES PATENTS 7/1970 Walsh 313/274 923,797 6/1909 McNeill 3 1 3/274 3,497,752 2/1970 Peterson 313/274 X 3,211,941 10/1965 Sanden et al.. 313/274 X 2,064,490 12/1936 Noble 313/274 Primary ExaminerRudolph V. Rolinec Assistant Examiner-Saxfield Chatmon, Jr. Attorney-Norman J. OMalley et al.

[57] ABSTRACT 3 Claims, 7 Drawing Figures TUBULAR INCANDESCENT LAMP HAVING IMPROVED FILAMENT SUPPORT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to tubular electric incandescent lamps having an axially extending coiled filament and particularly to intermediate filament sup ports in such lamps.

2. Description ofthe Prior Art Intermediate filament supports for lamps of the type to which this invention relates generally comprise two types of supports, disc spacers and wire ring supports. Examples of the former are shown in U. S. Pat. Nos. 2,813,993, 2,830,217, 2,910,605, 2,945,978, 2,980,820 and 3,160,777. Examples of the latterare shown in U. S. Pat. Nos. 1,125,121, 2,342,044, 2,864,025, 2,883,571, 3,132,278, 3,160,454, 3,168,670, 3,194,999, 3,195,000, 3,225,247, 3,240,975 and 3,364,376.

Disadvantages of the wire ring supports are a cooling effect caused by the wire knot required to lock the support to the filament and the shading of the filament by a the wire that spirals out to the envelope. In the case of the disc support, any deviation from perpendicularity to the filament will cause shading. Moreover, some filaments consist of two or more wires wound in parallel. Fastening discsupports to this type of filament is difficult and unreliable.

When incandescent lamps are used in photocopy equipment, the cooling effect on the lamp filament or the shading effect of spacers produces uneven distribu tion of lamp radiation on the surface exposed.

This uneven distribution is not desirable, but when a lamp is mounted close to the exposed surface or when a reflector is used to concentrate the lamp output on the exposed surface, uneven distribution becomes unacceptable.

It is an object of this invention to provide a filament support which substantially reduces uneven distribution of lamp radiation.

SUMMARY OF THE INVENTION the envelope walls. Preferably there are three such intertwisted legs, forming a wye shape, which substantially prevent any radial movement of the filament within the envelope.

The diameter of each wire of the support member is greater than the space between turns of the coiled filament in order to provide a wedging effect of said wire in said space. However, said diameter should not exceed the sum of said space between turns plus about 1% filament wire diameters in order to prevent any support wire from shorting out more than two turns of the filament.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of a lamp in accordance with this invention.

FIG. 2 is a cross-sectional view thereof, showing the shape of a support member.

FIGS. 3 to 7 show various stages in the formation of one embodiment of a support member in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a lamp in accordance with this invention comprises a tubular glass envelope 1 having press seals 2 at each end thereof. Axially disposed within envelope 1 is a coiled filament 3 connected at its ends to molybdenum ribbons 4 which are embedded within press seals 2. External lead-in wires 5 are connected to ribbons 4 and permit electrical energization of the lamp by connection to a suitable electrical power source.

Supporting filaments 3 are one or more intermediate support members 6, each comprising a plurality of intertwisted wires. Each support member 6 supports filament 3 axially within envelope 1, the ends of the intertwisted wires comprising support member 6 bearing radially against the inner wall of envelope 1, as shown in FIG. 2.

In one example of a lamp in accordance with this invention, a 1,350 watt, 1 15 volt, T2 16 type, the lamp had an overall length of 13 inches and an effective filament length of 10 inches. Filament 3 had a diameter of 46 mils and was wound from two 10 mil tungsten wires in parallel on a 26 mil mandrel at 44 turns per inch. The space between turns was about 3 mils.

Twelve support members 6 were used to position and support filament 3 within envelope 1, the support members being spaced about nine-tenth inch apart. Each support member 6. consisted of three 10 mil tantalum wires and was made as shown in FIGS. 3 to 7. First, two of the wires,A and B, were bent to angles of about 120 and placed on filament 3, somewhat opposite each other as shown in FIG. 3. The wires were placed in the space between turns of the filament and partially wedged therein. One leg of wire A was then intertwisted with the leg of wire B that extended in the same general direction, until said legswere substantially entirely intertwisted together, as shown in FIG. 4. Next, the third wire, wire C, was similarly bent and placed against filament 3 so that its legs extended in the same general direction as the untwisted legs of wires A and B respectively, as shown in FIG. 5. One leg of wire C was then intertwisted with wire B, FIG. 6, and the other leg was then intertwisted with wire A to form a wye shaped support as shown in FIG. 7. The intertwisted legs of the wye support were then cut off at a distance of mils from the filament surface which permitted filament 3, with support members 6 thereon, to be inserted into envelope 1 during lamp manufacture, as shown in FIG. 2. However, the length of the intertwisted legs of support member 6 was sufficient to prevent substantially any radial movement of filament 3 within envelope 1 throughout the normal operating life of the lamp.

We claim: Q

1. A double ended electric incandescent lamp comprising: a tubular envelope having press seals at its ends; a helically coiled wire filament longitudinally disposed within said envelope and electrically connected to lead-in wires extending externally from said press seals; and intermediate wye shaped support members axially supporting said filament within said envelope,

said support members comprising a plurality of intertwisted wires, each wire partially encircling said filament so that said plurality completely encircles and secures said filament, each of said intertwisted wires being partially wedged in the space between turns of 

1. A double ended electric incandescent lamp comprising: a tubular envelope having press seals at its ends; a helically coiled wire filament longitudinally disposed within said envelope and electrically connected to lead-in wires extending externally from said press seals; and intermediate wye shaped support members axially supporting said filament within said envelope, said support members comprising a plurality of intertwisted wires, each wire partially encircling said filament so that said plurality completely encircles and secures said filament, each of said intertwisted wires being partially wedged in the space between turns of said helically coiled filaments, the ends of said intertwisted wires bearing radially against said envelope.
 2. The lamp of claim 1 wherein the diameter of each of said intertwisted wires is greater than the space between turns of said helically coiled filament.
 3. The lamp of claim 2 wherein the diameter of each of said intertwisted wires is less than the sum of said space between turns plus 1 1/2 filament wire diameters. 